Perishing of vinyl componentsAugust 29 2017 at 6:03 PM
|Stuart Wilson (Login stuartwilson)|
from IP address 220.127.116.11
Hi, I posting this in the "modern" DG just because it pertains to a modern AFV but it could go anywhere.
I keep my finished kits in boxes as I don't have the display space. I opened a box today with two complete Takom Chieftains in it when I saw the front of the turret of one had developed a satin sheen. Removing the turret showed an oily substance on the turret rim that seems to come from the vinyl mantlet cover. This has so far only affected one kit but that was the first completed. What shocked me the most was the fact that this residue had covered the whole front of the turret, basically the Stilbrew area. It seemed to wipe off ok and looks better once I rubbed a tissue over it but I wasn't too keen on the idea of having to clean it off. Has anyone else experienced this?
Depends on what is going on
|August 30 2017, 9:19 AM |
If the material itself is degrading (like DS tracks, for example) then you can't save it. if it is actually "vinyl" that can not be painted with solvent based paints, which will react with the plastic and cause an oily sticky sufrace. That is why if you build vinyl figure models etc those must be painted with acrylic paints.
Sometimes you get similar reactions to poorly cast resin parts (cheap or poorly mixed resins) that leach out oils forever and will bleed through paint. That stuff will also melt plastic.
Maybe your experience, not everyones.
|August 30 2017, 3:07 PM |
I have DS tracks I painted with enamels 7 or 8 years ago. They have not degraded, broke, crumbled, whatever over that time. I think most the problems people have with DS type parts comes from what they weathered them with.
Gary I had trouble with UNPAINTED, untreated DS tracks.
|August 30 2017, 5:43 PM |
Sherman and StuG, some oozing, getting brittle and broke like glass with the slightest handling.
I'm not the only one, many modellers experienced this, there are several threads on Armorama, Missing Lynx, FaceBook groups...
Guess I'm just one lucky guy.
|August 30 2017, 11:01 PM |
I've never had any problems with anything DS.
|Pawel "Vodnik" Krupowicz|
|August 31 2017, 2:49 AM |
The DS material is not bad "by design". If manufactured correctly it should be as durable as styrene or vinyl (the real one, not the rubbery stuff some Chinese manufacturers were using in the past). And in majority of cases DS tracks really work well.
The problem is that DS seems to be difficult to manufacture correctly and the manufacturing QA in Dragon's Chinese factories apparently isn't particularly good... The end result is a noticeable percentage of bad quality products
that makes sense
|August 31 2017, 7:35 AM |
I've said before I thought that since the problem seems random and not in every kit, that it may be a formulation/mixing problem and that different production runs may have different mixes of the ingredients and sometimes it isn't right. Sort of the way you can have a badly mixed batch of resin that doesn't cure properly.
One of my Dragon Shermans in 1/72nd scale had this issue
|September 1 2017, 10:19 AM |
Never got around to building it and when I opened the box, the tracks had broken into smaller pieces.
Not just mine
|August 31 2017, 7:33 AM |
Maybe you haven't had the problem but many other people have. And its not just on this page or this forum but pretty much every armor forum.
I have opened brand new, sealed, store bought, kits and found the "soft" tracks to be a dark orange color, hard as a rock, and brittle. So, any deterioration has nothing to do with what you weather something with if they can go bad in a sealed box.
Likewise I have some Tamiya Churchill tracks that have done the same thing. They crack and split if you try to bend them around the wheels. They haven't even been painted. It's the newer gluable material from a current kit. The old vinyl ones don't have this problem.
I had this problem with old Dragon vinyl tires
|August 30 2017, 9:55 AM |
on my BTR and BRDM kits I built in the early 90s. The next time I tackled an armor kit with vinyl parts, I dipped the parts in Future floor polish (yes, I know it isn't a polish). Then I weathered the tires, or more accurately, I weathered the acrylic coating. I haven't had an issue with the vinyl tires melting like I did previously.
Issues with softer plastics
|August 31 2017, 11:54 AM |
Issues like this with softer plastics aren't uncommon. They're not universal, just not uncommon.
The primary contributor to this are the additives mixed, or compounded, with the base polymer and then moulded into the parts of the kit.
For instance, raw, pure polystyrene is the brittle, clear plastic used for clear parts and canopies. All the colours in kits are additives. The varying hardness we all know exists between different manufacturers and kits are also a function of different additives compounded with the base polymer. Others are added to increase mouldability, decrease shrinkage, etc. etc.
When it comes to the flexible plastics like vinyl or DS this is achieved through additives called plasticizers, adding plasticity (flexibility) to the base polymer. These, like all of these additives, come in a bewildering and ever-changing number of types and effects.
Now this would all be much more manageable if this sort of thing was strictly controlled. But, outside stuff bought to aerospace/defense/nuclear specifications (and paid for on that basis) these things are not terribly well controlled at all. Lots of times the compounder changes the additives to suit themselves (it's a touch cheaper or allows other additives to be inserted, etc.) and other times the moulder wants something a bit cheaper or easier (=cheaper) and they both simply make the changes they want and as long as there isn't a gross effect on the product, no-one's the wiser.
But sometimes there is an effect and it takes time to show up. Plasticizers, especially, have a tendency to leach out of the moulded product over time sometimes on their own, and sometimes in response to environmental conditions like heat, light or the presence of other chemicals. Plasticizer leaching out can leave a film on the object or on objects it touches. It can leave a product stiff, brittle and prone to cracking/splitting. It can also leach out of one product and into another making it look like the other product is "melting" if it is susceptible to that plasticizer.
The softer a part is, the more plasticizer it generally contains. The more, or more aggressive, at any rate. The more plasticizer a part has, the more likely it may be unstable over time.
Commercial compounders don't really check for this sort of thing and make no guarantees. If it happens, it happens and you're stuck. They also don't generally guarantee that their particular compound recipe won't change over time so a part that was good, may be not good for a while and then may go back to being good again. And it's entirely possible that no-one in the chain knows or cares why. It's a good bet that the compound recipe will change on a reissued kit, especially if several years have passed.
All of this is to provide some perspective on why this sort of thing happens and yet doesn't happen to everyone or every time.
Personally, I tend to avoid the flexible products on my models. I've had good luck with old school vinyl track, but avoid the flexible mantlet covers or DS track or soft truck tires simply because I feel the risk of leaching plasticizer is too high and I don't want to take a chance. If a new kit comes with flexible parts I now bag them separately to prevent contact and frequently don't use them in the end.
Here endeth the epistle...
Astounding insight ...
|August 31 2017, 12:14 PM |
I would just like to say "thank you" for that indepth overview of these plastic modeling components.
Very few of us have full insight into the industry, and every little report like this is a godsend.
Once again Thanks
Thanksfor the advive from all who replied
|August 31 2017, 12:46 PM |
I'll be a bit more careful before I use vinyl parts again.
A similar issues causes tire burn
|August 31 2017, 6:42 PM |
When tracks or tires melt the styrene. When Moebius Models issued their Lost in Space chariot, the rubber tracks and wheels attacked the plastic kit parts so quickly that brand new kits hot off the boat from China had bad melting and marring (since the rubber and styrene parts were in the same bags). Moebius couldn't figure out what caused the problem at first, since the rubber and plastic were the same ones used by another company (that I guess shares the same molding outfit in China). And none of the test shots and sample kits that Moebius had worked with ever had the melt issue. It turns out that the production kits had an aluminum powder additive (as I recall) to give the plastic a metallic silver look. Something in the additive caused the reaction. The solution was to just issue the kit in grey plastic.
Not only in 1/35 scale neither, also 1/6 scale
|September 2 2017, 9:05 AM |
I have my Swimwagen that the whatever they used to make the rubber tires has melted the rims.
A big deal as now one would have to buy a set of Resin tires that cost as much as the kit did, to fix that problem.
Also as the same tires used on the Sand fat rubber tires of the Kubel, also in 1/6 scale, but might of beat that as I applied a coat of Future to all the rims where the wheels are, almost impossible to remove these tires, I tried on The Swim a no go.
So not only just on DS tracks but what they used to make the vinyl, I would guess a chemical reaction. All Dragon of cause. Maybe reason why they through the towel in on large 1/6 scale stuff.
Dragon DS Wheels
|September 1 2017, 10:24 AM |
I have just had a delivery of a Dragon 6774 25pdr Field Gun and Limber and the four tyres are contained in a clear plastic package. The tyres have all "melted"/ "fused" together and onto the packaging. It may be the clear plastic bag that has caused the problem but the "tyres" are now unusable.
Soft Plastic Issues and an old school workaround
|September 6 2017, 2:53 PM |
The issue of shiny residue (the plasticizer mentioned in other responses) is an old problem. Back in the '60's and 70's, when dinosaurs walked the Earth, modelers who wanted to paint up the Airfix 1/32nd scale vinyl figures encountered this issue, and the solution at the time was to add a barrier coat of thinned PVA glue (white glue). This allowed them to paint the figures using Humbrol enamels, without the paint going shiny over time.
We also had the problem of vinyl and styrene reacting chemically. The 1/76th scale Airfix tank kits circa 1970 were known for their "rot-a-tracks" which would attack the styrene road wheels before turning into a sticky mess in short order. Airfix reformulated the vinyl after customer complaints, and the problem disappeared.
There have been frequent problems with Italeri's vinyl tires attacking styrene over the years, but again, the formulation problem appears intermittent, affecting some product runs while others are unaffected. The solution there was either a barrier coat, or a literal barrier, using Bare Metal adhesive aluminum foil on the tire rims to prevent the styrene and vinyl from touching. Curiously, the vinyl used on Italeri tank track was completely inert (at least in my experience).
I have never had a problem with the Tamiya vinyl track, though the glueable vinyl-styrene blend Tamiya introduced in 1997 is much less reliable, as it crumbles when exposed to enamels or lacquer thinner, and can break spontaneously where it has been bent (even in the box).
Dragon DS styrene hasn't degraded on any kits I've built or have in my stash, but the litany of problems seems to be increasing of late, and suggests a quality control issue with their suppliers, as others have mentioned. The only sure workaround would be after market styrene, resin or metal replacements.
|This message has been edited by GeraldOwens from IP address 18.104.22.168 on Sep 6, 2017 3:28 PM|